Rate of rise-dive indicator



P. B. LEVITT ET AL RATE OF RISE-DIVE INDICATOR May 19, 1953 '3 Sheets-Sheet 1 Filed May 25, 1947 John HTTURNE).

May 19, 1953 P. B. LEVlTT EI'AL RATE OF RISE-DIVE INDICATOR 3 Sheets-Sheet 2 Filed May 23, 1947 llullll i -II i i i ill-l i illllllll i y 19, 1953 P. B. LEVITT ETAL 2,638,786

RATE OF RISE-DIVE INDICATOR Flled May 25, 1947 3 Sheets-Sheet 3 INVENTOR. John fl. Morgan Percy 3.1.6 In! Patented May 19, 1953 RATE or RISE-DIVE INDICATOR Percy B. Levitt, Millburn, and John D. Morgan, South Orange, N. J., assignors, by mesne assignments, to Cities Service Research and Development Company, New York, N. Y., a corporation of New Jersey Application May 23, 1947, Serial No. 750,100

2 Claims. 1

This invention relates to navigational instruments, and more particularly to an improved device for indicating the rate at which a submarine vessel is diving from or rising towards the surface of the sea.

The conventional depth gauges with which every submarine is equipped serve to indicate the depth at which the vessel lies at any given time. Obviously as the vessel changes position there is a corresponding change in the depth gauge reading, a fact which is taken advantage of by experienced crewmen to gain some very rough approximation of the rate at whichthat change is taking place. In the absence of any better guide, this very rough correlation of time and changing elevation has had. to suflice, but that it has been a far from satisfactory criterior is detailed in the histories of submarines which have been lost by reason of the inability of the crew to prevent the vessel from breaking surface at just the wrong time, or to hover far below surface during enemy action.

Inour Patent 2,412,740, we have described an instrument for indicating the rate at which a submarine is diving from, or rising towards the waters surface, data which gives an accurate basis for the application by submarine crewmen of that degree of elevational control which is necessary to hold the vessel at a given level, or

to rise or dive at a speed which, may be kept within safe limits. This device has proven sufficiently sensitive and accurate to make it a highly valuable adjunct to conventional depth gauges in submarine navigation work. Service experience has demonstrated, however, that the inimmediately noted. The lack of a ready means i for adjustingthe zero position of the instrument has also given rise to operational troubles; and the use of an overly delicate pointer operating mechanism has made for trouble both in the manufacture of the instrument and, at times, in its usage.

, The principal object of the present invention is to provide a rate of risesdive indicator which is extremely sensitive in indicating very small rates of change of vertical position of a, submarine vessel, and which returns very promptly and accurately to its zero position when that vessel is riding at a constant depth. s

It is a further object to provide an instrument of the foregoingkind which operates over an expanded scale in the immediate vicinity of its zero position so that very small rates of change are indicated with great precision and accuracy; and wherein the higher, and consequently less critical rates of change are indicated upon a contracted scale, so that the overall range of the instrument may be as great as is desired without requiring a scale of excessive length. This means that we can employ a circular scale which for the sake of clarity is marked off in one direction from the zero point to indicate rates of dive, and in the other direction from zero to indicate rates of rise, and that each part of the scale can be confined to less than 180, so that there need be no overlapping with its likelihood of confusion in reading.

Further objects of the invention are to provide a rate of dive-rise measuring device hav ing'an actuating mechanism which may be manufactured easily and at comparatively low cost; one in which provision is made for simple and ready adjustment of the zero position of its indicator mechanism whereby to correct for any permanent deformation which the operating parts may have taken in normal usage; and generally to provide a device of this kind which is of more rugged construction and of greater precision in its operation and which lends itself more readily to duplication by conventional manufacturing operations than the device of our earlier patent.

The fullnjatiire of our invention and of the manner in which the foregoing and other of its objects may beattained, will be more fully understood from a consideration of the following description of one practical embodiment of it, as shown in the accompanying drawings, in which:

Fig. 1 is an elevational view, partly in plan, and partly'in section, of a preferred form. of indicating instrumentin which various details of both its rate measuring and indicating mechanisms are clearly shown;

Fig. 2 is an elevational view, on an enlarged scale, of the indicator mechanism of the instrument of Fig. 1;

Fig. 3 is a sectional view taken on the line 33 of Fig. 2;

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 2; i

Fig. 5 is a sectional view taken on the line 55 :of Fig. 2; r i

Fig. 6 is an end elevational view of the instrument of Figs. 1 to 5 inclusive, but on a some- What reduced scale, showing the indicating pointer of the unit and the calibrated scale over which it sweeps to indicate rates of rise and dive.

The instrument shown in Figs. 1 to 6 is of the unitary type, having its rate measuring and indicating mechanisms joined together in one compact assemblywhich is adapted to :be imounted in a submarine vessel in such positions that dial it and indicating pointer H are readily visible to the navigating officer and his crew. In the preferred form of instrument (Fig. 1), casing l2 provided with a threaded opening 1 3, for receiving a line (not shown) leading tothe outside of the vessel so that chamber M, will .be filled with sea water at a pressure corresponding to the hydrostatic head acting upon the submarines hull. Since this pressure may vary from a few to several hundred feetof water, depending upon the depth at which the vessel is operating at any given time, it is evident that the-casing must be of suitably rugged construction. We find it convenientto cast the element of bronze, a metal-which is substantially unaffected by sea water, although other corrosion-resistant metals may be employed and may be formed up'in any suitable way. It is of particular note'that the casing has a vent "55 through which airmay be allowed to escape during the initial filling of chamber Hi with sea water. Under normal operating conditions, vent i .is of course .closed tightly by asuitable plug [5.

One wall of chamber l-ll includes a spring supported diaphragm which is adapted to be ,displaced to aagreater or lesser'extent, depending uponthe pressure appliedto it. In the'preferred embodiment, this diaphragm element takes the formof a bellows ll which is secured in leak-tight relation .to cover plate 18, and which has its outerend closed and sealed by a cap 59. The supporting spring so, confined between cover plate it cap l9, tends to hold the bellows in a distended position against the'force of sea water which is acting on the outside of the latter element. It will be evident that the strength and stiffness of the spring must be gauged in terms of the overall range of the instrument, and of the maximum operating depth at which-the instrument is intended to function. The illustrated instrument, forexample, is designed for operation at all depths up to 200 ft, and spring Ml is of a stiffness appropriate to that operating range. In order to prevent excessive displacement'oi the bellows, and the destruction of its supporting spring when the vessel dives below the 200 ft. level, we provide a stop element in the form of a tube 2! mounted on cover plate is within spring 263 so that its free may engage and support the cap 19 when the pressure in chamber is rises to excessive values. We may also-provide a valve arrangement, as shown in our earlier patent, for'auto- 'matically shutting off communication between chamber Hi and the open sea when pressure conditions exceed some predetermined safe value.

The inside of bellows I-l forms a part of a liquid filled system having a ifixedorifice therein which serves to measure the rate of change of pressure in chamber .14. Thiszchange, of course, reflects the corresponding change in pressureon the hull of the vessel, andis therefore a measure of the rate at which the vessel is diving :from or rising towards the surface of the sea. Beferring again t Fig. 1, it will be noted that the system includes bellows I'l, conduit 2.3 in cover platelii, conduit 2a in body element25, of which one branch, Zia, .leads through a fixed orifice {the orifice on a linear scale.

- in that special parts do not have to be formed .andrassembledsandofmaking for ease of calibra- 7131011 dither-finished device by reason of the fact thatrthe totaliresistance of the orifice may be varied :by:me1:e adjustment of its length. It is ofiurtlrer notethat the orifice tube terminates on thebottomeofbsump 26 and at substantially the geometric center of that element, an arrangement which minimizes the eiTect upon the system of changes in head of liquid in sump 25 resultin .irem the tilting of the :instrument as the submarine dives or :rolls.

The sump element of 'Ethe illustrated unit 118 an .oblong sheet .metal box having a relatively large circular opening 30 .the ,zforward end of ,itsitop surrounded by 28, :fiange r3, which is adapted :to .fit against the underside tof body 25 with acced ng asket :32 .betweenthe opposing surfaces, and to besecured in .that position by screws -33 which passthrough the .box and 133% threaded :into .the .body. iProper .operation of the...device requires that the liquid in sump 26 shall -,be subjected at .all times .to atmospheric pressure, ..a requirement 'which vis .metiby the provision of a vent tube .34 .eXtendi-ng'irom the bottom .of .sump .25 yup through @the opening so that .it terminates .very ,close to the underside of body r25. This arrangement obviously minimizes the possibility: of .losing liquid through the vent opening .as a result .of any rsloshing which may occur ,in .sump .25. A plunged opening 3:5, shown in dotted lines .in.the.farTside-wallofthe sump as viewed in ,Fig. :1, servesasia means for adding liquid to the sump or for draining off excess .as .occasiOn may require.

Ilhesecond branch, MD, of the conduit in body '25 terminates in ,a threaded opening which is adapted to receive -a coupling 36.n1'ounted upon .theend of .a tube 31 leading .to .the-expansible element .38 of the pressure indicating mechanism. .It will be observed that :this latter element is bellows which has been found 2130 be somewhat easier .to make and to duplicate, and to be somewhat moresatisfactory in its response to ve y low pressure changes in the liquid ,systerm than the small volume, .:low spring itest 'Bourdon tube employed in the instrument which is .ill ust,1:ate d and described .in our earlier pat- ,ent. Referring to Figs. .2 .and it will be observed that the bellows is secured in leak-tight relation to a bracket 39,, mounted upon a circular sup orting .plate 40 and having a passage 41 leading from the inside .of the bellows .to an enlarged (opening 42 within the end .of ube 13. is sweated or otherwise fixed. The .free end of bellows '38 is closed and sealed by a relatively stiff element-A3,, the {latter having .a dependent tab 44 which is secured to an upstanding tab 4'5 on pivotally mounted bar 46. Inorder to avoid thehi-gh and variable friction which is associated with jewel and similar types of bearings, we preferably .secure the right hand end of bar 46 (as viewed in Fig. 2) to a bracket .41 mounted .on plate 4.0,, :by a thin and highly flexible strip-of spring metal '48, the ends of the strip being secured to the end of bar 45 and to bracket 41 by screws 49 or in any other convenient way. In the illustrated device, pivot link 48 is a strip of beryllium copper measuring about 1" X A" x .007, which has proven to be rugged enough for the purpose and to offer so little friction to the limited movement involved as to be substantially negligible. It is of further note that whatever resistance to movement pivot strip 48 may offer is of uniform character, unlike that of jewel or other types of bearings.

Any movement imparted to bar 45 by the expansion and contraction of bellows 38, in a manner later to be considered, is transmitted directly by link 50 to crank arm 5| on shaft 52,

the latter being journaled at its opposite ends in bearings in supporting plate 40 and bracket '53. It will be observed (Figs. 2-3-4) that shaft 52 carries a multiplying sector 54 which is meshed with a pinion 55 mounted upon a pointer shaft 56, the latter being journaled in bracket 51 and in plate 40 through which it extends to receive the indicating pointer II. The teeth of the multiplying sector, and of pinion 55, are made with great precision, but it is not always possible to form them so nicely that they will always be in perfect mesh. In order to avoid any backlash we prefer to engage pinion 55 with a second sector 58 mounted upon a shaft 59, journaled in supporting plate 40 and in bracket 60, and to provide a hair spring 6| which applies a slight torque to shaft 59 to hold the teeth of sector 54 and sector 58 in constant mesh with pinion 55.

The foregoing description of the major operating parts of our indicating instrument, and of the constructional details and arrangement of these parts in one preferred embodiment, forms a sufiicient basis for the description of the operating principles of the device. Other constructional details and features will be taken up in the course of describing such operation. By way of preface, it will be assumed that the liquid system has been completely filled, that is to say, bellows ll, bellows 38, the several connectng passages, and orifice 21 have been fully evacuated and filled with a liquid of appropriate viscosity characteristics, and that sump 26 I has also been filled with that liquid to the level indicated in Fig. 1. It is further assumed that the instrument has been installed in a submarine vessel, that its chamber M has been connected to the outside of the vessel, and has been vented of air and filled with sea water so that the pressure therein will correspond to the hydrostatic head acting on the vessels hull.

In such circumstances, when the vessel is lying upon the surface, the pressure in chamber I4 is no more than a few feet of water, and suffices to displace bellows H to the left, as viewed in Fig. 1, only to a limited extent. The system is therefore in balance with the pressure in chamber I4 exactly offset by the reactionpf spring 20, plus atmospheric pressure act ng upon the liquid in sump 26. As soon as a d1ve is started, however, the pressure in chamber [4 rises in direct reflection of the increasing hydrostatic head acting upon the vessel, and accordingly in direct indication of the depth at which that vessel lies at any given instant. The forces acting on cap l9 are thus thrown out of balance, the pressure applied by the sea water to cap I9 tending to force that element to the left, as viewed in Fig. 1, against the reaction of spring 20 and of the resistance which orifice 21 offers to the displacement of liquid from bellows 1! through the system into sump 26. It

follows that there can be no instantaneous equilibrium of the forces acting on the cap, and that the pressure in the liquid filled system will build up to whatever value is required to overcome the resistance 'of the orifice. This pressure rise is measured by the expansion of bellows 38, and the movement which it imparts through pivot bar 46, multiplying sector 54 and pinion 55 to pointer II. If the dive is a rapid one, for example, the pressure in chamber l4 builds up at a rapid rate, and tend to displace bellows I! to the left as rapidly as orifiice 21 will allow liquid to be expelled from the system into the sump. The pressure needed to maintain flow through the orifice will necessarily be high, and the indicating pointer I I will accord ingly be swept across the face of dial II] to indicate that the dive is taking place ata high rate. In the course of a less sharp dive, however, the pressure will build up in chamber l4 at a less rapid rate, and one which more nearly approaches that at which the liquid can flow from the system through the restricting orifice. It follows that the pressure drop across theorifice will be smaller than was true in the case first assumed, and that the deflection of pointer H will be correspondingly less, indicating, of course, that the dive is taking place at a'lesser rate. As the vessel levels oil? at some selected depth, it will be apparent that the pressure in chamber I4 quickly reaches a staticvalue corresponding to that depth. In these circumstances the fiow of liquidfrom the bellows rapidly drops oif until such time as the pressure of sea water acting upon cap [9 is just exactly balanced by the reaction of spring 20. Concurrently, of course, the pressure in the liquid filled system falls off, allowing pointer II to swing back towards its ,zero mark. At that point at which equilibrium is just reached, flow ceases, the pressure in the liquid filled system drops to zero, and the tip of pointer II will stand .opposite the zero mark on dial III to indicate that there is no tendency on the part of the vessel towards further dive.

So much, then, for the operation of the instrument to indicate rates of dive. Assuming now that the vessel starts to rise from the depth at which it leveled off, itwill be evident that this change must be reflected by a decrease in the hydrostatic head acting upon bellows I! in chamber H. The balanced condition which was discussed above will therefore, be immediately destroyed, spring 20 in this case acting to distend the bellows and move cap I 9 to the right as viewed in Fig. 1. Under these circumstances liquid is forced by atmospheric pressure from sump 26 into the system to maintain bellows ll completely filled. Such flow will, however, be resisted by orifice 21, so that the pressure in the liquid system falls below that acting upon the liquid in the sump, that is to say, below atmospheric. Bellows 38 will collapse to reflect this pressure difference, and will swing pointer II in a clockwise direction as viewed in Fig. 6 to indicate that the vessel is rising In this case, the pressure which is built up across orifice 21 will be in proportion to the rate at which bellows I1 is expanding in an effort to equalize the forces acting upon the opposite sides of cap l9. If the rise is a gradual one, a correspondingly smaller pressure difference will be required to maintain flow of liquid from the sump into the system, and the subatmospherlc pressure within bellows 138 will be such as to produce a correspondingly sma-l-ler movement of pointer l l. Conversely, a rapid-rise of the submarine, and a correspondingly rapid falling off of hydrostatic pressure in chamber M, will result in the building :up of a relatively large pressure difference across orifice 21, and pointer II will be deflected a correspondingly large amount.

It will be evident to those familiar with the art that orifice 2-1, by restricting the flow of liquid between bellows H and sump 2-6, introduces "a time factor into the system; and that the pressure drop across the orifice is a measure of the rate :at which pressure "in chamber [4 is changing, rather than of the actual pressure in that chamber, and accordingly, of the rate of rising or diving of the vessel. Since this pressure drop is accurately measured by bellows 38, it follows that dial Ill may be graduated in terms of feet per second of rise'on one side of its zero point, 'a-nclpf feet per second of dive on thepther side of that neutral mark.

The utility of an "instrument of this kind is largely dependent upon its sensitivity to small changes in pressure in its liquid filled system, and to the speed with which it responds to those changes. Thus the illustrated "device is adapted to respond to achange in pressure in chamber- 14 as of little as two 'to three inches 'of water, and of equal importance, to reflect that change within a very small fraction of a sec-- end. The accurate measuring of very low rates of rise or dive is obviously a matter of major importance, and particularly so when the vessel is cruising just below the surface, or when it is hovering at some fairly great depth under the control of changing ballast rather than its diving planes. We accordinglyprefer to make our instrument most sensitive in it operation in the immediate vicinity of its zero mark; in fact, we prefer to employ expanded scale operation for 'a short distance on each side of the neutral mark. In order to accomplish this, we fix a leaf spring element 65 (Fig. 2) in the 'free end of bar 46, as for example by screw 66, and extend that spring outwardlybetween the spaced lugs *6"? of a bracket 53 which is mounted on the rear side of supporting plate M! by means of screws "'59. The, screws I'll which are threaded in lugs 67 in opposing relation, form stop elements for spring 55 and accordingly limit its free movement. Assuming that these parts are in the positions shown in Fig. 2, with spring '65 lying midway between the ends of stop screws Hi, "the other parts of the instrument lie in such relation that the top-of pointer 'l-I stands opposite the zero mark on dial it. Any movement of bar '46 under such conditions is opposed primarily by the spring effect of bellows 3B, the -reaction of pivot link -d8, and of hair spring 6!, being by comparison so slight as to be negligible. Pointer vll is therefore free to swing a relatively large distance in response to the building up of a relatively small pressure in bellows 38, until such time as spring 65 engages one or the other of the stop screws Ill. When that occurs, the tension of spring -65 is brought into play,to supplement the spring tension of bellows 33. Under such circumstances it follows that pressures acting on bellows 38 are opposed by a much heavier spring tension, and accordingly result in smaller movement of pointer H across the face of dial l0. In the illustrated instrument, stops T are so adjusted as to allow for exceptionally sensitive movement, and accordingly expanded scale operation within a range of from zero to :6 feet per second by the rise or olive, and a very much less sensitive and contracted scale operation within the range of from .6 to 8 feet per second.

It will be observed (Fig. 2) that lugs '57 carry a second pair of stop elements ll which are so arranged as to overlie and underlie the free end of bar 46 to limit the movement of that element. In the illustrated device each of these stops has a toe portion extending at rig-ht angles to its main body to present a small and well defined abutment to bar 38. Other form ofstepa-andalternate arrangements for their mounting in the instrument, will'readily suggest themselves to those skilled in the art. The important thing here is not the form and construction of the elements, but the function which they perform; namely, to limit the movement of bar it so that the deflection of pointer M will not materially exceed full scale reading in either direction. In this connection is of particular note that the stops are applied to bar it, rather than to some other part of the moving system, for the express purpose of relieving the linkage fill lii, multiplying sector 5 and pinion 55, and the indicating pointer H, of the strain which would be imposed upon these parts in a rise or dive at a rate in excess of that for which the instrument is designed. Thus when a submari-ne crash dives, its rate of descent far exceeds the :8 feet per second maximum scale reading for which this particular instrument has been designed. Under such circumstances, movement-of bar 46 is limitedbythe lower one of stops H so that no excessive stress can be transmitted to the other and more delicate parts of the indicating mechanism.

It is a further factor of major importance in an instrument of this kind that the 'indicating'pointer shall return promptly and precisely to its zero mark, and that there shall be no sluggishness of its action when the vessel is leveling bit. This is partially accon'siplished in the illustrated instrument by the provision of expanded scale operation the immediate vicinity of zero as heretofore described. Adequate sensitivity in this respect i also assured by the use of indicating forces which are large by comparison with pivot friction and the other opposing forces in the indicating system. It will be observed, for example, that in this instrument we employ a bellows 3B which is very large by comparison with the Bourdon tube of the instrument disclosed in our earlier patent, so that the forces acting upon the indicating gear train are proportionately large. We further find that the addition of sector '58 and hair spring'fi! to the gear train, to eliminate backlash is also very helpful in assuring a prompt and accurate zero indication. We have further improved the instrument in this regard b the provision of a zero adjusting mechanism. Thus, as is best shown in Figs. '2, 3, alight spring 12 is connected between the lower end of link 50, and a crank arm 13 mounted on gearl l, which latteris 'journaled upon a pillar "E5, on the rear of plate m. The tension which spring l2 applies to the system may be adjusted by rotation of shaft 16 and pinion 64 mounted on its rear end, that pinion being meshed with gear "it as best shown in Fig. 2. If in the course of operation there is any permanent deformation of bellows 38, pivot lin'k d8, leaf spring 65 Or of any of the parts of the mechanical train between the bellows and indicatingjpointer shaft 56, with a correspondingshift in the position which the pointer 9 H takes when the system is in balance, the entire system can be returned to the initial zero setting by an increase or decrease of the tension which the adjusting spring 12 applies to the moving parts. In this connection it will be noted that a spring 11, held in compression between the rear side of supporting plate 40 and a collar 18 on shaft 16, tends to hold the enlarged head portion 19 of that shaft in frictional engagement with the recessed portion of the front side of plate 40, to maintain spring 12 under any adjusted tension, and that the forward end of head 19 extendsthrough an opening in plate l0, and is slotted to receive a screw driver to facilitate zero adjustment from the face of the instrument.

It will be apparent that the resistance which orifice 21 offers to the flow of fluid in the liquid system will depend upon its own size and length, and upon the viscosity of the liquid employed in the system. Furthermore it will be apparent that any substantial change in the viscosity of the liquid will affect the pressures which are built up across the orifice under different operating conditions, and accordingly, the indication of rates of dive or rise. We prefer therefore to employ a liquid which has a comparatively fiat viscositytemperature characteristic, so that it will not become unduly thick or thin with changes in temperature. In this connection we have found that a silicone fluid having a viscosity of about centistokes at 25 centigrade performs very satisfactorily in the illustrated unit. The solution of about 47.75% of tricresyl phosphate, about 42% of ethylene glycol monobenzylether, about triethylene glycol, di-2 ethylbutyrate and about 0.25% by weight of rust inhibitor, described in our earlier Patent No. 2,412,740, is also suited to the requirements of an instrument of this kind. We do not intend to imply that our invention is limited to the use of either of these fluids, however, for others having appropriately flat viscosity temperature characteristics may exist or may be prepared; and in any event an absolutely flat viscosity may be attained by providing suitable heating equipment which will maintain the temperature of the liquid at a constant value.

It will be observed that the several essential parts of the instrument of Figs. 1 to 6 inclusive are so designed and arranged as to facilitate manufacture and assembly. Thus, the several parts of the displacement mechanism, i. e., bellows l1, cap l9, spring 20, and stop tube 2! may be independently formed and assembled upon cover plate I8, giving a sub-assembly adapted to be slipped into chamber l4 with a gasket 80 forming aleak-tight seal between the cover plate and a flange 8| on casing I2. The indicating mechanism may be built up upon supporting plate 4|] as previously described, and that sub-assembly may then be set into the front of body 25 and secured in place by suitable screws (not shown) as is illustrated in Fig. 1. The graduated dial l0 may then be fitted into the flanged portion 82 of body 25 and fixed in place by screws or in any other suitable way, after which pointer l I may be mounted on the end of pointer shaft 56, and the face of the instrument covered by dial glass 83 'which is fixed in place between suitable gaskets 84 and a bezel 85, screws 86 serving to secure the latter to the body 25. These two major subassemblies may then be brought together, with conduit 23 in cover [8 aligned with conduit 24 in body 25, and the whole assembly secured together by screws 81 or in any other suitable way. The liquid system may be evacuated and filled with a 10 selected liquid, and thesump affixed to the body in the manner heretofore described.

The unitary instrument which is shown in the drawings has much to commend it. Its several casing [2, cover plate l8, and the several parts carried by the latter element may be assembled as a unit, separate and apart from the assembled indicating mechanism and the sump; and these two sub units maythen be mounted on. a submarine vessel in. locations remote from one another and connected only by a conduit which represents no more than an extension 23 and 24. i

It will be-observed that the instrument shown in theqdrawings has been designed andbuilt to indicate diving or rising within a fairly wide range of from zero to eight feet per second, and at all depths up to 200 feet below the surface. Obviously, however, the operatingrange may be very much increased to include even crash diving rates, or it may be decreased to any desired extent, as for example, by a mere variation of the stiffness of spring 65 which opposes movement of the pressure sensitive bellows element 38. So, too, that part of the operating range which is indicated on an expanded scale may be increased or decreased by an adjustment of stop screws Til and an appropriate remarking of scale I0. Again, the instrument may be built for operation at much greater depths, say at 400 or more feet below surface, in line with present trends in submarine work, by the use of an appropriately rugged displacement bellows IT, and an appropriately rated spring 20. It will also be apparent that the form and arrangement of spring 65, and its associated stop elements it], which provide for expandedcontracted scale operation, may be varied from that which has been shown for illustrative purposes.

It will be observed that our instrument functions basically as an indicator of the rate at which the pressure applied to its displacement diaphragm ll is changing. In the illustrated embodiment, the pressure in question is that of the open sea at various depths, a measure of the change of rate at which a submarine vessel is diving or rising. Those familiar with the art will readily recognize, however, that our instrument may be employed for measuring changing pressure under substantially any circumstances, as for example, the discharge of a pump, in the outlet of a standpipe or reservoir system, etc.

Having described our invention in its broader aspects, and. illustrated it by way of specific example, what we claim as new and useful is:

1. A pressure gauge comprising a pressure sensitive member which is adapted to be displaced in proportion to pressure applied to its interior, means for connecting said member to a pressure system, a multiplying sector, a pivotally mounted bar attached to said pressure sensitive member and connecting the member and the sector, a pinion meshed with the sector, a shaft driven by of passages h p nion a poinie earned b the shaii, a second- Sector meshed. nmima hai. wr n 9on1 nes e i sai second se t r, and, servin to, hold 99th 91' the se iqrs mes ed with he in n a leaf spr g mqunt d n he fore end oi said. pivote all-y rrgounued bar, a pair ofspa edsio elements i posed n'o pgs e id s i said ea spr said st p el m n e vi t9 a iv. iree mpvemeni of.- sa d her an pressu e s nsitive elements within pre rm ned mits and to cause aidsprin to 999;??? u h. movem ni b yond Said limits, a sew 0nd pair of; stop mer ts rnqunted in opposin relaqipr or; op-pgsite sides oi saidbarv to, limit mqyemeni efthe bar a nd pressure,sensitivememe he a 61, Spring coppepted at one of its endslto saidbar. and means copnected to the other end f; sai oil sp in tor vary n the te n p t said ba t ad ust; the. zem. position fsaid P355 1176. SfiQSifiYQ member and Qfisaid. pointer.

2- A lasessure. au e qomprising a pressure. sen-4 sitiye member wl igh is adapted to be. displaced in prgpgrtip tq pressure applied. to its interior,

n; fg qg negting saidhmemhenta a pressure; ysie a multiplyin sectQr, a pivotally mountedbar attached to said pressure sensitive. member iid cqnneqtine the, member and. the. sector, a piriivori IIIQShfiQXYiQI thesestor, a shaft driven by theipiniqn winter carried. by theshaft; a leaf spring mp r ted in the; tore ends of isaidi pivotally- Ql pfi bar, ain fspaced stop. elements dispQfiQd 01 posite. ides Qf..-s aidi1eaf spring, said tep elements. serving to allqw free movement of said. bar: and; pr ssure sens t ve elements wi hin predetermined limits, and 00 cause said spring to. oppp se such meyement beyond said limits, a coilspring cqnneeted. at one of its endsuov saidbar and means connected to the other end of said coil spring for varying the tension applied tov said bar to adjust the; zero position of said pressure sensitive member and o f; aid pointer.

PERCY B. LEVITT. JOHN G. MORGAN.

Rfifsrgn es Cited n he fil of t s. patent U lTE TES. PATENTS Number Name Date 1,187,738 Janney June 20, 1916 1, 289,71-2= Evans Dec. 31, 1918 1,809,898 Heise June 16, 1931 1,869.,934 Doser Aug. 2 1932' 2,054,911 Newell et a1 Sept. 22, 1936 2:,05-7Q576 Johnson Oct. 13, 1936 2,176,807 Wunsch Oct. 17, 1939 2,284,588 i Rineer May- 26', 1942 2,412,740 Morgan et al Dec. 175L946- 2 ,43l,098 Wallace NOV. 18, 1-947 FOREIG PATENTS Number Country Date.

32 Great- Britain 1904A i 5,, France May 29, 1913v 

